tmf : fix the 'Not' condition in TmfXmlCondition

tmf : fix the 'Not' condition in TmfXmlCondition

Now, a 'Not' condition "Not X" will create a subcondition using its
first children instead of itself; which was actually creating the
condition "X".
Also, this patch update TmfXmlConditionTest to validate the fix.

Change-Id: I5b14d345c652a8eb553728c56ba6933b87a56ddd
Signed-off-by: Jean-Christian Kouame <jean-christian.kouame@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/64309
Reviewed-by: Hudson CI
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>